Protective transformer arrangement



March 26, 1946. H. s. GATES ETAL 2,397,099

PROTECTIVE TRANSFORMER ARRANGEIENT Filed May 26, 1942 3 Sheets-Sheet 1 MAE/9 ATTOR NEY March 26, 1946. GATES r 2,397,099

PROTECTIVE TRANSFORMER ARRANGEMENT Filed May 26, 1942 3 Sheets-Sheet 2 AMA/fa, 6d

WITNESSES: INVENTOR5 j/Znes. 72;, 4% 5 3242 ATTORNEY Patented Mar. 26, 1946 PROTECTIVE TRANSFORMER ARRANGEMENT Henry S. Gates, Sharon, and Henry D. James,

Edgewood, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 26, 1942, Serial No. 444,508

7 Claims.

The invention relates to electrical apparatus such as transformers, and particularly to aircooled, air-insulated network transformers for use in electrical network distribution systems.

Network distribution transformers are widely employed for supplying electric energy to areas having high load densities and include, in general, a network circuit of interconnected distribution circuit conductors supplied with electric energy through a plurality of transformers from a plurality of feeder circuits. Certain of the net work transformers are connected to be supplied from certain of the feeder circuits and other transformers are connected to be supplied from other of the feeder circuits. When a fault occurs on one of the feeder circuits, the faulty feeder circuit, together with the network transformers connected to the circuit are removed from service. The network circuit or distribution circuit supplied through the transformers continues to operate, receiving electric energy from the network transformers that are connected to and supplied from the other feeder circuits. A characteristic of this system is that substantially n interruption of service results because of a faulty feeder circuit, which may be withdrawn from service.

In prior art network systems, it has been customary to provide network transformers having substantial reserve or spare capacity. The necessity for this requirement will be appreciated when we realize that all of the transformers connected to one feeder circuit may be removed from service at the same time. In the case of a network circuit having two primary feeder circuits, it is necessary when one of the feeder circuits is removed from service that the entire network circuit be energized from the network transformers associated with the remaining feeder circuit. Thus, the entire load is supplied through one-half of the transformers. With a larger number of feeder circuits the proportion of total capacity to be removed from service upon the failure of one circuit is proportionally reduced but the same principle applies.

In prior network transformers, it has been the practice to employ core and coil assemblies enclosed in tanks or casings connected to the feeder circuits and distribution circuit through terminal conductors that are welded to the conductors of these connected circuits. Such transformers include a switch on the primary side of the transformer between the windings and the feeder circult and a network protector switch between the secondary transformer windings and the load circuit to which they are connected. In disconnecting such a transformer from the line when it becomes necessary to remove it and'replace it with another, it is necessary to provide means for deenergizing both the high-voltage and low-voltage circuit conductors leading to the transformer in order to permit the severing of the welded circuit connections. This disconnecting of the transformers becomes a considerable undertaking.

unless additional high voltage and low voltage switches are provided as separate pieces of apparatus so as to sectionalize the transformer from the circuit.

In Patent 2,300,465, to John S. Parsons, issued November 3, 1942 for improvement in Electrical distribution systems, a network distribution system is described in which the network transformer units are provided with switching means which permit the connection of each network transformer to any one of a plurality of feeder circuits. In such a system, after a fault occurring on one feeder circuit, the transformer units connected to it may, by the operation of such switching means, be connected to other feeder circuits still in service so as not to lose the service of the transformer i normally associated with the faulty feeder circuit except for a relatively short duration of time.

It is an object of the invention to provide an air-cooled, air-insulated, network transformer for use in a system of the above-indicated character in which the core and coil assembly may be readily disconnected from the unit and removed from the housing without the necessity of interrupting the permanent connections between the unit and the primary or secondary circuits connected thereto.

It is a further object of the invention to provide for removing the core and coil assembly by sliding the same through an opening provided in the side wall of the unit housing in a manner not to disturb the other parts of the unit, thus making it possible to replace the core and coil assembly of the unit.

Other objects and advantages of the invention will be apparent from the following description of the embodiment of the invention in which:

Figure 1 is a perspective view of a transformer unit organized in accordance with the invention;

Fig. 2 is a diagrammatic representation of the main circuits employed;

Fig. 3 is a side elevational view, parts being broken away and other parts being shown diagrammatically;

Fig. 4 is a top plan view of the core and coil assembly of the unit; and I Fig. is an enlarged elevational view, partly in section as shown by line VV in Fig. 3.

Referring to the drawings, and in particular to Fig. 1 thereof, a housing I is provided having a continuous sheet metal top 2 with downwardly extending flanges adjacent the edges and a similar sheet metal bottom 3 having upwardly extending flanges adjacent the edges, the top and bottom being joined by vertical steel supporting members 4 spaced from the ends of the casing structure and such additional supporting members 5 as required to add suflicient rigidity to the housing structure. The remaining portion of the housing structure consists of parts formed of metal mesh 6 and includes a pair of doors 1 formed of this material, a portion of one being shown adjacent the corner of the casing nearest the observer in Fig. 1. Two such doors run from top to bottom of the near end of the casing which encloses a network protector assembly 8.

At the other end of the housing is provided a twoposition selector switch it, the operating han dle of which is shown at 8, for connecting the high-voltage windings of the transformer to one set of terminals II or to a different set of terminals I2 which are permanently connected to two seperate primary feeder circuits. The lowvoltage terminals I3 of the unit are mounted on the top of the unit above the network protector 8 to which the three-phase conductors l4 lead from the network protector switch l5 within th housing of the network protector 8. The side wall portion of the housing between the upright members 4 is of similar wire mesh material as the remainder of the housing wall, and is omitted in Fig. 1 so as to more clearly illustrate the apparatus in the housing. The core and coil assembly I6 of the transformer is assembled in this central part of the housing, and is shown as a three-phase transformer having three separate winding legs about each of which are positioned primary and secondary windings. This core and coil assembly is mounted upon base plates I! which rest upon I-beams or similar rails I8 to which they may be fastened by bolts 19. The I-beam rail or track members I8 run transversely of the floor of the housing so as to permit relatively easy movement of the core and coil assembly sidewise from the housing after disconnecting the conductors in a manner to be later described.

Referring particularly to Figs. 1, 3 and 5, the three-phase transformer, core and coil assembly I6 illustrated comprises a core structure 3| provided with three vertically positioned legs 32 connected by horizontal top and bottom yoke portions 33 and 34 clamped between channel members 35 by bolts 36 which provide end frames for the core structure. Upper and lower steel pressure plates or rings 3! and 38, respectively, are provided for assisting and holding a lowvoltage winding 39 and a high-voltage winding 4| in their proper positions about the winding leg of the core structure. The lower pressure plates 38 are supported from the channel irons 35 upon angle iron members 42 and insulating strips 43.

The outer winding is supported from the pressure plate by porcelain blocks 44 at top and bottom, the blocks being spaced about the edge of the winding so as to bring pressure to a stack of coils 45 comprising the winding structure which are separated by porcelain blocks 46 which serve as spacing and insulating members. The stack of coils and spacer blocks, together with the end blocks 44, are held tightly in place between the pressure plates 31 and 38 to which pressure may be applied by the bolts 41 (see Fig. 5) connected between the upper pressure plate and the upper end frame channel members 35. The inner or low-voltage winding 39 may comprise a plurality of cylindrical coils 48 wound about the inner central tube 48 of noncombustible insulating material, the tube and coils extending the whole distance between the upper and lower pressure plates 3! and 3B.

The winding is made up of two parallel strands or bars, the ends 5| and 62 of which are united in a bus bar 53 forming one terminal conductor, and the ends 54 and 55 uniting in the bus bar 56 to form the other outlet from the winding. The other two phase windings are similarly connected, one end of each low-voltage winding being connected to the lower bus bar 53 which is grounded, and the upper end being connected to bus bars 51 and 58 as best shown in Figs. 1 and 3. The bus bars 56, 51 and 58 follow along the top of the core and coil structure and down wardly to the rear of the network protector cabi net 8 containing the switch l5. The bus bars 56, 51 and 58 are attached by bolts or similar separable couplings 6i (see Fig. 3) to the network protector panel. The high-voltage windings are connected in delta and through circuit conductors shown generally at 62. The ends of these conductors nearest the transfer switch ID are mounted on bushings 63 supported from the upper end frame of the transformer structure. Connecting jumpers 64 are provided extending to the bushings 65 mounted on a shelf 66 on the rear panel of the transfer switch Ill. The jumpers 65 are connected through separable couplings 51 to the switch terminals. An insulating barrier 68 is provided, which is shown mounted upon the upright members 4 between the connecting jumpers 64 and the live parts 69 of the switch I0 to prevent contact with live parts of the circuit in disconnecting the jumpers 64 when the switch II] is in its open position.

It will be noted that the complete structure of the transformer core and coil assembly, together with the terminal conductors mounted on the end frame structure may be readily removed from the transformer unit by disconnecting the highvoltage leads at the couplings 61 on the rear panel of the transfer switch and disconnecting the lowvoltage bus bars at the couplings M on the rear of the network protector panel, and removing the structure of sliding it sidewise of the housing, that is lengthwise of the I-beams I8. In order to do this, the bolts I8 which hold the structure within the casing are removed, and preferably members similar to I8 are positioned on the outside of the housing in line with the members I8, to receive the base plates I'I, so that the base plates I1 and the structure mounted thereon may be slid from the track within the housing to a similar track outside the housing upon which it may be moved to its desired destination. It is unnecessary to disconnect the terminals II, I2 and I3 of the unit from their terminal conductors in order to make this change of core and coil assembly. Before the couplings SI and 61 are disconnected, the unit will be deenergized by first opening the breaker I5 of the network protector and by then operating the transfer switch I0 to its open circuit position. A similar core and coil assembly may replace the one removed in a short time and service through the unit continue without the necessity of disconnecting the unit itself from the primary and secondary circuits. The handling of the core and coil assembly by removing it through the side of the housing is much simpler than where it is necessary to raise the apparatus by the use of a crane. In the illustrated structure, the cover is a solid sheet metal cover, so that it would not be possible to remove the core and coil assembly by raising it from its position, and in many places where such transformers are used, the head space above the transformer is too limited to permit raising the transformer core and coil assembly from the unit. Lugs H are provided in the bottom end frame to which tackle blocks or other means may be attached for the drawing of the unit along the I-beams I8 out of or into the housing I. The side wall portions of the housing between the vertical members 4 on both sides of the housing are similar and are both removable so that the core and coil structure may be slid into the housing from either side.

Fig. 2 of the drawings shows diagrammatically the general arrangement of the apparatus and circuits of a transformer unit organized in accordance with the invention and including the removable core and coil assembly 16. This assembly includes the high-voltage windings 4| that are connected in delta relation to each other and through the selector switch Hi to the selected feeder circuit connected to the terminals II or I2 of the unit. The low-voltage windings 39 are connected in Y relation between a grounded metal bus 53 and phase bus bars 56, 51, and 58 which are connected through the network protector switch I5 to the low-voltage terminals l3 of the unit.

The network protector 8 includes, in addition to the protector switch [5, a closing motor or solenoid 8|. The switch is normally held closed by a tripping latch 82 which is operated by a tripping solenoid 83 as controlled by a master relay B4 and a phasing relay 85 which, since they are not a part of the present invention, are not described in great detail in this application, but are described at greater length in the above-identified application of John S. Parsons, Serial No.

418,729 for improvement in Electrical distribution systems, filed November 12, 1941.

The switch is interlocked with the network protector switch i by an interlocking rod 86 which is provided with a finger 81 for preventing operation of the switch Ill except when the switch is open and the rod 85 is pressed against the spring 88 so as to release the finger 81 from engagement with looking member 89 of the switch l0.

It will be obvious to one skilled in the art that many modifications of the details of construction described may be made by the spirit of the invention, and we do not wish to be limited otherwise than by the scope of the appended claims.

We claim as our invention:

1. In an electrical distribution unit having a housing containing an air-cooled air-insulated transformer core and coil assembly provided with primary and secondary windings, the side walls of the housing having openings for the ingress and egress of air into and from the housing, a plurality of sets of high-voltage terminals for connection to a like number of feeder circuits, in combination, switch means for selectively connecting the primary windings to any set of said terminals, and a protector switch for interrupting the connection of said transformer core and coil assembly to a load circuit when the direction of energy flow through the transformer reverses, separable connectors between the switch means and the primary windings and separable connectors between the protector and the secondary windings, and means for removably mounting said transformer core and coil assembly for ready removal from the housing.

2. In an electrical distribution unit having a housing containing an air-cooled, air-insulated transformer core and coil assembly, the side walls of the housing having openings for the ingress and egress of air into and from the housing, and two switch means mounted on opposite sides of the core and coil assembly for connecting the coils of the assembly, respectively, to incoming feeder circuit conductors and outgoing load circuit conductors, in combination, separable connectors between each of said switch means and the windings of the core and coil assembly for readily disconnecting the apparatus from the circuit conductors for removal from the housing, a portion of the side wall of the housing being removable, a track within the housing, and means for mounting the transformer core and coil as sembly on the track for ready removal from the unit through the opening provided upon removal of the portion of the side wall of the housing.

3. In an electrical distribution unit, an elongated housing, high-voltage terminals for the unit mounted at one end of the housing, low-voltage terminalsfor the unit mounted at the other end of the housing, in combination, supporting members running transversely of the housing, openings in the side walls of the housing opposite the supporting members, a transformer core and coil assembly having primary and secondary windings mounted on the supporting members within the housing, a transfer switch for connecting the high-voltage terminals to the primary windings. a network protector switch for connecting the secondary windings to the low-voltage terminals and for interrupting the connection of the transformer to the low-voltage terminals when the direction of energy flow through the transformer reverses, and separable connectors between the transfer switch and the primary windings and between the protector switch and the secondary windings.

4. In an electrical distribution unit having anelongated housing having a continuous sheet top and bottom and openings in the side walls thereof, high-voltage terminals adjacent one end of the housing for connecting the unit to a feeder circuit, a transfer switch mounted within the said end of the housing for connecting the high-voltage terminals to an electrical apparatus within the casing, low-voltage terminals adjacent the other end of the housing for connecting the unit to a distribution circuit, a protector switch within said end of said housing for connecting the lowvoltage terminals to an electrical apparatus within the casing, in combination, a track structure within the housing comprising rails extending across the central portion of the housing, a transformer core and coil assembly apparatus having primary and secondary windings connected through said high-voltage and low-voltage switches, respectively, mounted on the track structure between two switches, separable connectors included within the circuit connections between the apparatus windings and the switches to readily disconnect the apparatus windings from the switches for removal of the core and coil assembly from the housing, and openings in the opposite sides of the housing of suflicient size and so located as to permit the core and coil assembly to pass from the housing along said track structure through said openings.

5. In an electrical distribution unit having an elongated housing, high-voltage terminals extending from the housing adjacent one end thereof, low-voltage terminals extending from the housing adjacent the other end thereof, a transformer core and. coil assembly within the housing having primary and secondary windings, in combination, switch means for connecting the primary windings to the high-voltage terminals, switch means for connecting the low-voltage windings to the low-voltage terminals, means for ready removal of the core and coil assembly from the distribution unit comprising separable connectors between the high-voltage switch and the primary windings, separable connectors between the low-voltage switch and the secondary windings, and openings in the opposite sides of the housing of sufficient size to permit assembled core and coil structure to pass therethrough.

' 6. In an electrical distribution unit having an elongated housing containing an air-cooled airinsulated transformer core and coil assembly having primary and secondary windings, highvoltage terminal conductors for the unit extending through the top of the housing at one end and low-voltage terminal conductors for the unit at the other end of the housing, in combination, a transfer switch for connecting the high-voltage terminal conductors to the primary windings, a network protector switch for connecting the secondary windings to the low-voltage terminals and for interrupting the connection of the transformer to the low-voltage terminals when the direction of energy flow through the transformer reverses, supporting members within the housing running transversely of the housing for supporting the core, openings in the side walls of the housing opposite the supporting members for permitting the core and coil assembly to be removed through the side wall of the housing, highvoltage separable connectors connected between the transfer switch and the primary windings and extending from above the core and coil assembly downwardly along the side of the transfer switch, and an insulating barrier extending downwardly from adjacent the top of the housing between the high-voltage separable connectors and the high-voltage terminal conductors of the unit.

7. In an electrical distribution unit, an elongated housin having openings in the side walls thereof, high-voltage terminal conductors for the unit, a transfer switch mounted within one end of the housing for connecting the unit to said terminal conductors, a protector switch mounted within the other end of the housing for connecting the unit to a distribution circuit and for interrupting the connection of the unit to the circuit when the direction of energy flow through the unit reverses, in combination, a track structure within the housing extending across the central portion of the housing between the openings in the side walls of the housing, a transformer core and coil assembly having primary and secondary windings mounted on the track structure between the openings and between the two switches and provided with primary and secondary terminal conductors positioned above the core and coil structure and connected through separable connectors to said switches, the separable connectors for connecting the high-voltage winding terminal conductors to said transfer switch extending downwardly from adjacent the top of the housing along the side of the transfer switch, and an insulating barrier extending downwardly from adjacent the top of the housing between the high-voltage separable connectors and the high-voltage terminal conductors.

HENRY S. GATES.

HENRY D. JAMES. 

